Multi-Protocol Label Switching (MPLS), as defined in RFCs 3031 and 3032, describes an architectural framework that supports a variety of network services. MPLS Transport Profile (MPLS-TP) is a profile of MPLS that is targeted at the transport domain of an MPLS network. MPLS-TP also defines an architectural framework for delivering network services.
An access network is a part of a telecommunications network that connects subscribers to their immediate service providers. An access network can be contrasted with a core network, which connects service providers to each other. An access network is generally a transport domain and is suitable for deploying MPLS-TP. However, a core network generally deploys MPLS, Internet Protocol (IP), or a combination of MPLS and IP. Due to the different protocols used in these two network domains, an interworking layer is typically implemented at the boundary between the two domains to facilitate the inter-domain communications. This interworking layer can be designed as a third architecture or layer, such as a Virtual Local Area Network (VLAN), as is typical the case in handoffs between two network domains. However, this third architecture or layer can introduce a new set of problems, such as a need for re-designing resiliency and operations, administration and maintenance (OAM), which can cause a significant increase both in capital expenditure and operating expenses of a telecommunications network.